A chemically synthesized oligonucleotide 20 residues in length containing the terminally repeated nucleotide sequence of Rous sarcoma virus 35S RNA has been prepared. This molecule is currently being used as a hybridization probe for studies of RSV proviral DNA and for sequence analysis of the junction between integrated RSV provirus and host cell (chicken) DNA. These studies are expected to reveal the nature of the integration site sequence. Sequence analysis studies of endogenous cDNA synthesized by detergent disrupted RSV virions are also proposed. These studies are expected to reveal detailed information concerning the reverse transcription of the viral RNA genome into a covalently closed circular double stranded provirus DNA structure.